Reconstructing Point Set Order Types from Radial Orderings

Abstract

We consider the problem of reconstructing the combinatorial structure of a set of [Formula: see text] points in the plane given partial information on the relative position of the points. This partial information consists of the radial ordering, for each of the [Formula: see text] points, of the [Formula: see text] other points around it. We show that this information is sufficient to reconstruct the chirotope, or labeled order type, of the point set, provided its convex hull has size at least four. Otherwise, we show that there can be as many as [Formula: see text] distinct chirotopes that are compatible with the partial information, and this bound is tight. Our proofs yield polynomial-time reconstruction algorithms. These results provide additional theoretical insights on previously studied problems related to robot navigation and visibility-based reconstruction.